The scientific tourist #117 — Mariner 5

This week, you get a pair of images — scans of photographs I took 20 years ago at JPL, of two different Mariner 5 models. The first, of a small display case model:

The second, of an engineering model (mockup) at full scale:

Mariner 5 was originally built as a backup to the Mariner 4 spacecraft sent to study Mars in 1964. But the Mariner 4 flyby went so well that Mariner 5 was refitted for service much nearer the Sun, and launched in 1967 to fly by Venus instead. It carried instruments to interplanetary and Venusian magnetic fields, charged particles, plasmas, and UV emissions of the Venusian atmosphere.

Mariner 5 found that Venus had only a very weak magnetic field, and no radiation belts trapped by it (unlike the situation at the Earth). Meanwhile, radio occultation data from the flyby indicated that the temperature at the surface was about 527 deg. C (980 Deg. F), and the pressure 75 to 100 times that at Earth’s surface — countering the Soviet claim that the Venera 4 spacecraft had survived to reach the surface.